A known storage system includes one controller box and one or more PDEV boxes each having a PCI-Express (PCIe) switch device. The controller box has a storage controller. The PDEV box has the PCI-Express (PCIe) switch device and a plurality of PDEVs connected to this PCIe switch device. In a storage system of this type, a controller box (storage controller) is connected to at least one PDEV box (PCIe switch device). The PDEV is a non-volatile physical storage device and, for example, is a hard disk drive (HDD) or a solid state drive (SSD). The PCIe switch device is a device that includes a switch function for relaying communications in accordance with an interface called PCIe. The storage controller accesses an access destination PDEV via a PCIe switch device to which this PDEV is connected.
Each PCIe switch device has a plurality of ports. The ports that the PCIe switch device has is hereinafter referred to as “SW port.” The SW ports include downstream ports (DSPs) connected to lower-level devices (here, lowerlevel switch devices) and upstream ports (USPs) connected to higher-level devices (here, higher-level switch devices or storage controller). The DSP is a port whose attribute is “downstream.” The USP is a port whose attribute is “upstream.”
As a known technique for setting the attributes of the SW ports, the technique disclosed in PTL 1 may be mentioned. According to PTL 1, a plurality of central processing unit (CPU) nodes are connected to each switch node (PCI switch device). A controller in the switch node defines any one of the SW ports to which the CPU node is connected as USP and defines the other SW ports as DSPs.